The present invention relates to the field of SCADA systems and more particularly to a SCADA system in which changes to properties at a site are pushed to users at remote locations to automatically update the human machine interface at the remote locations.
Supervisory control and data acquisition (SCADA) refers to large-scale distributed measurement and control systems. SCADA systems are used to monitor and/or control chemical, physical or transport processes, in municipal water supply systems, to control electric power distribution and generation, gas and oil pipelines, and other distributed processes. A SCADA system typically comprises: input/output signal hardware and controllers at the various sites to be monitored and/or controlled; a SCADA hub for monitoring and controlling the various sites; communication links from the various sites to the SCADA hub; and supervisory stations at locations remote from the SCADA hub in communication with the SCADA hub. A SCADA hub is often referred to as a Master Station.
Prior art systems typically operate under supervisory control from the SCADA hub. The input/output signal hardware at the various sites is often termed a remote terminal unit (RTU). The RTU at each site is in communication with one or more programmable logic controllers (PLCs), optionally to one or more Direct Data Controllers (DDC) and optionally to one or more of a variety of sensors and primarily functions to report properties of the various PLCs at the site to the SCADA hub and to adjust a set point of the various PLCs responsive to control commands received from the SCADA hub. While any and all of PLCs, DDCs and sensors may be utilized, for ease and clarity of explanation the term PLC is used throughout this document to include PLCs, DDC and sensors. Thus control of equipment at the site is controlled by the local PLC, and the RTU enables remote monitoring of properties and adjustment of a set point for the PLCs from the SCADA hub. Prior art systems typically poll the various RTUs from the SCADA hub thus uploading site property information.
The SCADA hub is equipped with a human machine interface (HMI) which presents site property data to a human operator, and through which the human operator controls the process of the various sites by adjusting set points of the PLCs as required. In a typical embodiment the HMI graphically presents the process at each of the various sites, and presents the properties of the PLCs in a graphical format. In order to alert the operator, colored indicators are typically supported to indicate nominal, cautionary and emergency conditions.
Setting up such a graphical support typically is accomplished by qualified engineering or technicians at the SCADA hub, based on information supplied by an integrator from a site visit. In particular, the HMI package typically includes a drawing program that the operator or system maintenance personnel use to prepare a graphical presentation of the properties of the PLCs to be reported from the RTU, and to enable control of the set points of the various PLCs via the RTU. Thus, the integrator functions at the site to physically configure the RTU, and to report on the configuration to the SCADA hub for conversion of the RTU based information to graphical representation. Such a system leads to a significant time lag between the site visit by the integrator and the availability of graphical representation at the SCADA hub.
It is further desirable to enable authorized personnel to review selected site properties and adjust selected set points remotely from the SCADA hub. One solution to this desire revolves around the preparation of a secured web site loaded with the appropriate HMI by the SCADA hub. Thus authorized personnel utilizing a web browser are able to access up to date information upon request from any location. Unfortunately, such solution has certain drawbacks. First, the solution requires the authorized personnel to request an update from the web browser in order to retrieve new information. Furthermore, changes at the site are not automatically reflected on the user's secured web site, since the SCADA hub polls various sites according to a predetermined schedule. Additionally, as described above, preparation of the graphical representation for the secured web site requires input from the integrator regarding properties and technical personnel to prepare the presentation.
Instant messaging (IM) is a form of communication that employs presence and availability technology as described, for example, in U.S. Pat. No. 7,123,695 the entire contents of which is incorporated herein by reference. In particular, an instant messaging network recognizes when a user is present on the network, and typically sends notification to other users when an additional user from a list becomes present on the network and available to receive instant messages. IM differs from e-mail in that text based conversations may happen in real time. Many features of e-mail, including persistency of the message, have been added to IM systems however they remain distinguished primarily by their notification of presence and availability.
What is needed, and not provided by the prior art, is a SCADA system in which changes in properties at a site are automatically transferred to a user at a location remote from the SCADA hub. Additionally, preferably the graphical representation of the site should be automatically presented without requiring technical personnel input, or requiring further input from the integrator on site.